| Trigger Effect
Trigger Effects (Japanese: 誘発効果 Yūhatsu Kōka) activate whenever a certain condition on the Field, the nature of play, or the progress of the turn, is met.
Trigger effects are considered to be Spell Speed 1, but that doesn't mean you can activate them when ever you want, only when the condition has been met. If Compulsory Trigger Effects or Optional Trigger Effects (that do not miss the timing) trigger at a time when they cannot be activated, such as if there exists a current chain, each effect that was triggered will start a new chain at the next opportunity afterwards that they can start a chain. For simultaneous activations, the order these effects are added to the start of the new chain follow the rulings for when Simultaneous Effects Go On the Chain (TCG currently handles the ordering differently than OCG.)
Optional Trigger Effects are effects that don't happen automatically when the trigger condition is fulfilled, the controlling player decides whether to activate it or not. These effects involve cards like "Mystic Tomato", "Peten the Dark Clown", or "Dark Magician of Chaos". With "When... you can..." Optional Trigger Effects it is possible to Miss the Timing. However, with Optional Trigger Effects, like ones with the structure, "If... you can...", the effect can be activated at the first possible opportunity to activate cards and effects after the trigger condition was met (skipping over any chain opportunities that forbid that particular effect from activating at that time, such as the Summon Negation Window.)
When two Optional Trigger Effects try to activate at the same time such as two copies of "Mystic Tomato" destroy each other in battle, neither will miss the timing, as the last thing to happen was both being sent to the Graveyard. Both of the effects trigger at the same time, and form a Chain. The Turn Player's effect becomes Chain Link 1, and the opponent's effect becomes Chain Link 2.
Only the activation of an Optional Trigger Effect can miss the timing. In other words, as long as the effect is activated, the resolution will never miss the timing. So two monsters will be summoned in the above example.
Compulsory Trigger Effects are effects that must resolve, and are not Optional.
Identifying Trigger Effects can be done, for cards made after PSCT change, by looking for a timing related condition, followed by a colon " : ". Some of these cards are not necessarily Trigger Effects, such as Ignition effects that are usually in the form "Once per turn: You can..." or "During your Main Phase: You can..." If you are not sure what type of effect(s) a card has, the information can be looked up. Note that cards like Obelisk the Tormentor with PSCT have the word "When" but don't have a colon. Instead, these usually denote conditions.
List of TCG and OCG Monsters with Trigger Effects
|Japanese name||Rank||Level||Attribute||Type||Card type||ATK||DEF|
|8-Claws Scorpion||八つ手サソリ||2||DARK||Insect||Effect Monster||300||200|
|Absolute Crusader||レアル・クルセイダー||4||EARTH||Warrior||Effect Monster||1,800||1,200|
|Absolute King Back Jack||絶対王 バック・ジャック||1||DARK||Fiend||Effect Monster||0||0|
|Absorbing Kid from the Sky||吸収天児||4||LIGHT||Fairy||Effect Monster||1,300||1,000|
|Achacha Archer||アチャチャアーチャー||3||FIRE||Warrior||Effect Monster||1,200||600|
|Adhesive Explosive||瞬着ボマー||3||WIND||Machine||Effect Monster||1,000||1,000|
|Aether, the Empowering Dragon||魔装聖龍 イーサルウェポン||6||LIGHT||Dragon||Effect Monster||2,300||1,600|
|Aethersatellarknight Zefra-Thuban||竜星因士－セフィラツバーン||4||LIGHT||Warrior||Pendulum Monster||0||2,100|
|… further results|